Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage assembly that retains a reticle, a projection optical assembly and a wafer stage assembly that retains a semiconductor wafer. With the exposure apparatus, the reticle stage assembly positions the reticle and the wafer stage assembly positions the wafer so that when the reticle is illuminated by the illumination source, an image from the reticle is projected onto the desired location on the wafer.
Typically, the wafer stage assembly includes a wafer stage base, a wafer stage that retains the wafer, and a wafer stage mover assembly that precisely positions the wafer stage and the wafer. Somewhat similarly, the reticle stage assembly includes a reticle stage base, a reticle stage that retains the reticle, and a reticle stage mover assembly that precisely positions the reticle stage and the reticle. The size of the features within the images transferred onto the wafer from the reticle is extremely small. Accordingly, the precise relative positioning of the wafer and the reticle is critical to the manufacturing of high density, semiconductor wafers.
Unfortunately, the wafer stage assembly can incorrectly position the wafer and/or the reticle stage assembly can incorrectly position the reticle. As a result thereof, an alignment error can exist between where the image from reticle is projected onto the wafer and the desired location for the image on the wafer. This degrades the accuracy of the exposure apparatus.
In light of the above, there is a need for device and method for accurately adjusting the projected image from the reticle. Additionally, there is a need for a device and method for compensating for alignment errors between the reticle and the wafer. Moreover, there is a need for an exposure apparatus capable of manufacturing precision devices such as high density, semiconductor wafers.